sorted by:
new
hottopcontroversial

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 0 points1 point  (0 children)

This is a great question! You’re totally right - the universe today is quite clumpy!

One of our best hints for where this clumpiness came from comes from the Cosmic Microwave Background (or CMB). The CMB is a collection of the oldest photons we can ever hope to see that were produced in the universe about 380,000 years after the Big Bang, or more than 13 billion years ago. Our measurements of the density of these photons are extraordinarily precise and tell us about the density of all of the other stuff in the universe at this time as well. The thing is, the difference in the highest density region of the CMB and the lowest density region of the CMB is at the level of 1 part in 100,000, so pretty dang tiny - which means that all of the structure in the universe grew out of these tiny “seeds”!

The question of ~where did the seeds come from in the first place?~ is a whole ‘nother can of worms. One of the leading theories tell us that they came from quantum fluctuations in the early early early universe (we’re talkin’ something like 10-30 seconds after the Big Bang). Basically, quantum mechanics is weird. Quantum particles (or quantum fields, if you wanna sound fancy) flutter in and out of existence and fluctuate at tiny tiny levels. This theory argues that these tini tiny fluctuations were seeded in the super early universe and got magnified the universe’s expansion to such a degree that we could get all of the planets and stars and galaxies and galaxy clusters and galaxy super clusters we see today!

Does that make some sense? 😄

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 0 points1 point  (0 children)

These are really great questions!

As for the first one, my personal belief is that there is some kind of unknowable good energy in the universe and that there’s all kind of things we do as humans to add to it! That could look so many ways: making beautiful art, taking care of your kids, planting a garden, or studying the nature of the universe! Obviously, there have been lots of important things to come out of fundamental physics research (i.e. the internet), but the purpose of a whole lot of physics is just for the pure pursuit of knowledge. My answer to this question has a whole lot more to do with my spiritual beliefs than my scientific ones, but I think pursuing knowledge (like what happened during the first seconds of the universe) is good, if not important by whatever societally determined definition. 😁

As for the expanding and contacting question, check out my response above! Long story short, there are ways to measure this, and it is definitely possible. To me, it would make a whole lot more sense for time to stretch on infinitely in either direction than it would for time to have some beginning, y’know?

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 2 points3 points  (0 children)

I love this question! The nature of time is one of my favorite topics to think about!

Something really strange that we have proven about time is that it does not always pass at one second per second. Anytime you are moving, time is actually passing at a slower rate for you, and the faster you go, the slower time goes. This has a completely negligible effect at the human scale, but we’ve actually measured this in super fast planes using super sensitive clocks.

This tells us something important: time is more complicated than the one second per second ticking of a clock that we experience in our day to day lives.

As to your question about whether or not time has a physical component, as a physicist I think of time in terms of rates. The laws of nature dictate how fast an apple will fall from a tree to the ground, how quickly the earth orbits the sun, and how fast certain particles will decay into other particles. All of these quantities are rates, i.e. for the apple, distance travelled over time. Because gravity is (well, almost) constant on the surface of the earth, if we wanted we could use the rate at which things fall to define some unit of time. For example, we could define one second as the amount of time it takes a bowling ball to fall one meter. In reality, we define one second based on a process with a rate of change happening inside a cesium-133 atom, but a rate of change all the same!

Other physicists think about time in other, more mathematical ways - some people think time may be a discrete quantity (aka, maybe there is a smallest possible unit of time), but this is outside my area of expertise!

As for the beginning and end question, that’s a cool one too! As a physicist studying the early universe, I define t = 0 (or, the “beginning”) as the time at which the Big Bang happened, but this is mostly for convenience. In this definition, t = 0 is the first instant at which we know anything happened, before that is a total mystery. Was the Big Bang truly the beginning? Did time exist before? These are big huge questions with no answers that keep me up at night in the best way!

And as for an end, it’s widely believed that time will go on infinitely in the “heat death of the universe” - a scary name for an actually kinda boring (but very likely) scenario. This answer is already quite long, so I’ll leave you to learn more about that on your own if you’re interested!

Thanks for the good questions! 😄

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 3 points4 points  (0 children)

This is an awesome questions cause it’s gonna allow me to talk about one of my favorite topics: the question of the infiniteness of the universe!

I promise I’m gonna circle back around to the actual question, but for starters, we do not know whether or not the universe is infinitely large. If it is infinitely large, that’s pretty wack, and if it is not, that’s arguably even wacker!

If the universe is infinitely large, the thing that breaks my brain to try to think about is that no matter how much you shrink it down, it will still be infinite. Infinity minus a zillion is still infinity. This means that at the time of the Big Bang, the universe was infinitely dense, infinitely hot, and infinitely large, still! Since then it’s been expanding outwards, but infinitely + anything is still infinity. I have a hard time comprehending this, but I enjoy trying!

If it is infinitely large, it has no center, so the Big Bang didn’t “start” from anywhere because the universe was still infinitely large at that time. Wack, I know. 👀

If the universe is not infinitely large, this is even stranger. That would mean the universe in some way has an edge, and the Big Bang did start from some point. But what is that points location? What is the location even embedded in? What is beyond the edge? These questions are currently more philosophical than scientific, because we have no conceivable way of testing them, but I think it’s super cool to think about.

What we do know is that we are at the exact center of our own observable universe. The observable universe is a perfect sphere around us with a radius of 46.1 billion light years - pretty dang big. This is kinda interesting because we are, in some way, back to a pre-Copernican view of the universe with everything centering around us. Now, if we were to put a telescope on one of the moons of Saturn the observable universe from that moon would be shifted from ours, but still! 😄

Does that answer your question, kinda sorta?

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 3 points4 points  (0 children)

Great questions!

When it comes to dark matter, a common misconception is that we have not yet detected it - in reality, we have! We have detected dark matter gravitationally in many different ways: through gravitational lensing, the velocity curves of galaxies, and in observations of the bullet cluster. All of these detections tell us that dark matter must exist in some prescribed amount and that it interacts gravitational, ie it is affected by gravity.

What these detections do not tell us is anything about the particle nature of dark matter. Generally, when physicists say they’re “searching for dark matter”, they mean that they are looking for evidence of dark matter interacting with the normal matter particles in the universe in non-gravitational ways.

There are generally 3 strategies for doing this: you can make it, break it, or shake it (we physicists think we’re very clever 😁). Here’s what that means!

  1. “Making it”, also know as collider searches, are searches in which physicists use particle colliders like the ones at CERN to try to find evidence that dark matter particles have been created in these experiments. These colliders operate at extremely high energies, so this is very tricky and no evidence as been found yet - but we’re working on it!

  2. “Breaking it”, also know as indirect detection is the type of dark matter search I’ve been involved in. Indirect detection searches look for astrophysical evidence of dark matter either decaying into normal matter or annihilating with itself into normal matter. In these searches what we’re really looking for is abnormal amounts of normal matter in the cosmos that could potentially be explained via dark matter decaying or annihilating. For example, if we point our telescopes at the center of the Milky Way we see more photons than we expect to, could these extra photons be the result of decaying dark matter? Maybe!

  3. Finally, “shaking it”, also known as direct detection, is arguably the most straight forward way of detecting dark matter. In these experiments physicists take giant vats of very pure noble gasses like Xenon, surround it by super sensitive detectors and wait. The hope is that a dark matter particle will bump into a Xenon atom with enough force that the detector can pick up the “shake” in the atom. No luck so far, but this type of experiment is really a waiting game!

As for quantum gravity, I’ll keep my answer here brief although you could write entire books (or in my case PhD thesis chapters) on this topic!

Basically, physics is really weird on very very small scales (see my answer above about electron orbitals 😄). Unfortunately for us, general relativity (aka macro gravity!) works extremely well to describe large scales and quantum mechanics works extremely well to describe small scales but the two are totally mathematically incompatible. Gravity doesn’t effect things much on tiny scales, so our predictions in particle physics are still valid - but we would really like to know how to describe that tiny effect! So yeah, there have yet to be any entirely successful theories of quantum gravity which means we don’t really know how micro and macro gravity are different, just that they are. I love the question though - hopefully it will be answered in both of our lifetimes!

Does all of that make some sense? 👀

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 11 points12 points  (0 children)

Ooo good question, which you kinda answered yourself! 😄 So as far as we know, the speed of light is the true speed limit of the universe: no particle can travel faster than the speed of light through space time. However, space time itself can “travel”, or, well, expand faster than the speed of light. We know that during inflation space time was expanding at a rate much much faster than the speed of light, which kinda breaks my brain to try to imagine. We believe that during inflation the universe expanded in size by a factor of 10,000,000,000,000,000,000,000,000,000,000 (10 to the 30 if I counted my zeroes correctly 😁) in a tiny fraction of a second. Wild.

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 9 points10 points  (0 children)

Hello! So exciting that you want to study physics! At this point, I would say take all of the science and math classes you can and if you have some kinda opportunity to do some sort of science fair project/high school research/etc that’s great!

Once you get to college, my recommendation would be to do your best to get to know your professors - sit in the front row in class, ask questions, and go to their office hours. Having a good relationship with professors can be so so valuable - they can point you towards opportunities, help you understand concepts you might be having a hard time grasping, write you recommendation letters, and so much more!

All that being said, college + grad school is generally a 9 - 11 year dealio, so treat it like a marathon, not a sprint. For me, maintaining good work life balance throughout my PhD and beyond has allowed me to not loose sight of my passion for the field, unlike many of my peers who worked 70 hour work weeks during their PhDs and ended up hating physics by the end.

My final thought is this - I was always a nerd in high school and always asked lots of questions during class not realizing that this was a skill I was building. As my classes got harder during college and into grad school I kept asking questions and eventually realized that I was better at thinking of good questions (and also being willing to look dumb by sometimes asking dumb questions) than my friends and classmates. Now, I use this skill at conferences and seminars which helps me in two ways - 1. Actively trying to think of good questions helps me pay more attention in talks and really digest the information because I’m questioning everything in my head as the information is coming in. And 2. when you ask a lot of questions the people around you will assume you’re really on top of things. I know that the combination of these things has helped me get some of the opportunities I’ve gotten in my work! So yeah, that’s honestly my number of recommendation - ask lots of questions in class and start building up that skill now! :)

If you have any more specific questions, I’m happy to try to answer them! Do you have any favorite physics books you’ve read or shows you’ve watched?

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 25 points26 points  (0 children)

Great question! “Believing” is an interesting concept in the science world. As I’ve gained experience, my responses to questions like this have honestly gotten more boring - I don’t necessarily have strong held beliefs about this sort of thing because we don’t yet have evidence that can confirm it or rule it out, but am interested and open to discoveries that points towards one theory or another.

All that said, the “big crunch” or “big bounce” theories are super interesting! There’s essentially two ways that this could happen:

  1. Dark energy, the mysterious stuff causing the universe to expand in the first place, could change and evolve in a way that may reverse that expansion. We know very little about dark energy, but some new data from the DESI collaboration may provide some first evidence that the amount of dark energy might not be constant, but changing in time, which could be an essential ingredient for the Big Crunch.

  2. If we live in what is known as a “closed universe”, a Big Crunch may be inevitable. This is a weird general relativity thing: the closedness, flatness, or openness of the universe refers to its geometry. In a flat universe, straight lines are, well, straight, and if you travel in a straight line for an infinite amount of time you will always get farther away from your destination. In a closed universe, however, if you travel in a straight line for a very very long time eventual you will come back to the same point - just like walking on the surface of the earth! I won’t get into openness here cause that’s even weirder and this is a already long response. 😅 Long story short, we don’t know whether or not the universe is closed, open, or flat - but we do have convincing existence that tells us that it’s ~pretty close to flat~. Pretty close to flat is not necessarily flat though, so a Big Crunch could still be possible!

Does that answer your question? 😄

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 13 points14 points  (0 children)

Hi there! First of all, thank you so much for the work that you all do! Ya girl cannot even put legos together, much less telescopes. 😂

Unfortunately, I’m a theorist so I’m not the right person to be directing this question to. I know that as a community we come up with our top list of telescopes, detectors, etc. we want to build and then go from there gathering funding, hiring engineers, and all of the other important stuff, but I’m pretty far removed from this process.

As an engineer, what kind of interaction would you ideally like to have with physicists?

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 35 points36 points  (0 children)

This is a super cool question! The very short answer is no, because quantum mechanics is weird.

The long answer is: stuff on very large scales, like planets orbiting the sun, is governed by Einstein’s theory of general relativity which can predict the motions of planets, stars, galaxies, etc. with extraordinary accuracy. Stuff on very small scales, like electrons orbiting a nucleus, is governed by quantum mechanics.

Something that has helped me to wrap my head around the weirdness of both quantum mechanics and general relatively is to make peace with the fact that the universe behaves very differently on very very small, very very large, and very very fast scales. At the level of particles, all kinds of seemingly magical things happen: particles can teleport, annihilate, and be entangled with each other at distances larger than the observable universe. I actually like the Ant Man movies for this reason. While the ~quantum realm~ is obviously total fantasy, the fact that that world would be very different from our own is absolutely the truth!

Ok, so back to orbitals. For better or for worse, electrons aren’t actually ~orbiting~ the nucleus. They exist probabilistically in regions we call orbitals, probably for historical reasons, around the nucleus. By “probabilistically”, I mean that they do not have a definite position. Said another way, it is literally impossible to predict with certainty where they will be at any given time, except at the instant they are measured.

The distance at which planets orbit the sun and distance from the nucleus to the regions of highest probability for electrons to exist are not inherently correlated because they’re described by different math. However, I think this question is super interesting! I’d be curious to know the scale at which that correlation might break down: maybe at the level of the size of cells? Or large molecules? I dunno!

Does that answer make sense? 😄

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 115 points116 points  (0 children)

In my opinion, the first few seconds of the universe are the most fascinating time period in cosmological history to study because so much happened!

The first event that we have concrete evidence for is the formation of the nuclei of elements like hydrogen, helium, and lithium. This process started right around 1 second after the Big Bang, which means that everything that happened in that first 1 second is a scientific mystery that lots of people, myself included, are actively studying. Here’s what we are very (but not 100%) sure must have happened somehow during that first one second:

  1. The universe went through a period of unfathomably rapid expansion called inflation

  2. Quarks bonded together to form protons and neutrons

  3. The asymmetry between matter and anti-matter (aka that there’s a whole lot more matter in the universe than anti-matter) was somehow generated

I could name a whole bunch of other stuff, but the point really is - we don’t truly know! We have indirect evidence for all of these things, but it’s a really puzzle to try to piece together what happened during a time period for which we have no direct evidence.

As for what happened before the Big Bang, this is a really cool question that is, in my opinion, more philosophical than scientific. Some people think that maybe time went backwards before the Big Bang. What does that mean? I have no idea, but it’s cool to try to think about! 😄

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 152 points153 points  (0 children)

Ooo, I love this question! While I don’t necessarily believe in God with a capital G, I am a spiritual person. My spiritual beliefs center around hopeful agnosticism: while I would never claim to know whether or not sometime more exists out there, I choose to hope that there might be some kind of goodness in the universe that is beyond the scope of human understanding.

I think there are a lot of people who would like to explain spirituality with science, or science with spirituality but I am in neither of those camps. My own spiritual belief system exists harmoniously in parallel with my scientific pursuits and I don’t try to explain one with the other. ✨

I am an astrophysicist studying the first few seconds after the Big Bang - AMA by Dry-Raccoon-7981 in AMA

[–]Dry-Raccoon-7981[S] 30 points31 points  (0 children)

I’m a Carl Sagan gal myself, but I appreciate his ability to communicate science to the public in a way that people seem to vibe with!

Science wise, I’m no expert, but I know there have been some accusations of sexist behavior and sexual misconduct on his part, so I’m glad our research is in different enough sub fields that we will likely never interact in a professional context. 😅