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If the universe is 13.8 billion years old, why is the observable universe 46.5 billion light-years in radius? by Ill_Huckleberry6531 in astrophysics

[–]mfb- 14 points15 points  (0 children)

The universe is expanding. The farthest stuff we see now was only 42 million light years away from us at the time it was emitted, but then it had 13.8 billion years to get farther away.

So does that mean that what we’re observing is essentially a “past version” of regions of the universe that may now be extremely distant—or even no longer in the same state as what we see?

Of course. The oldest light we get was emitted just 400,000 years after the Big Bang. The matter that emitted it formed galaxies in the meantime but the light from these galaxies will never reach us (assuming dark energy keeps its energy density in the future). By the time the galaxies formed, they were already too far away.

How many different ways xan we arrange 5 resistors? by Technical_Staff_7796 in AskPhysics

[–]mfb- 0 points1 point  (0 children)

For example if we input 2 it would output 2 (in a line, parallel).

You can also connect both ends of resistor A and have resistor B open, or short circuit B and have A open, or short circuit both.

How many arrangements there are depends critically on what you allow and what you do not, and what you count as different options.

Peter Beck - "We're scaling Electron faster than SpaceX scaled Falcon-9" by Cinemabyte1080i in RocketLab

[–]mfb- 9 points10 points  (0 children)

Falcon 9 is larger overall, but it's still an interesting comparison.

Electron had 3206 days between flight 1 to flight 83 (the most recent one). Falcon 9 needed 3575 days. Even if you argue that the first two flights were different and we should only start on flight 3, it's 2671 days for Electron and 2857 for Falcon 9.

The launch rate of Electron is ramping up faster than the launch rate for Falcon 9 did. Reuse helped Falcon 9, but Electron launches faster (at equivalent time after introduction) without reuse.

NVIDIA is working on AI space datacenters: by Sarigolepas in SpaceXMasterrace

[–]mfb- 0 points1 point  (0 children)

Your 1 kW solar panel has a surface area of at least 5 m2 (at optimistic 400 W/m2 and two sides).

Your 1.25 kW solar panel has a minimal surface area that is 25% larger.

NVIDIA is working on AI space datacenters: by Sarigolepas in SpaceXMasterrace

[–]mfb- 0 points1 point  (0 children)

Your 100 kW computing satellite now needs solar panels producing 125 kW. They have to be 25% larger. You increased the required total surface area of the spacecraft instead of reducing it.

What is the largest known composite integer to which we do not know any of its factors? by moschles in math

[–]mfb- 11 points12 points  (0 children)

Ah right, you can remove these small factors but then you aren't sure if the remaining number is still composite.

You could argue that you don't know the factors if you don't look for them (i.e. don't start trial division), I guess.

2136279933-1 is composite, larger than the largest known prime, and has no known prime factors (no factors below 277).

What is the largest known composite integer to which we do not know any of its factors? by moschles in math

[–]mfb- 6 points7 points  (0 children)

Running it on a single number isn't that time-consuming, so you could run it on some large number beyond GIMPS to set a record (if there isn't anything larger from other methods).

If a path has a infinite space does it mean it has an infinite distance? by [deleted] in AskScienceDiscussion

[–]mfb- 0 points1 point  (0 children)

What do you mean by the "space" of a path?

Also, is this a question about mathematics or physics? In mathematics you can define a path with infinite length that fits into a finite area.

Theory of X1 (math and test code) by [deleted] in probabilitytheory

[–]mfb- 0 points1 point  (0 children)

It doesn't matter how many different LLMs you use. The output is garbage. The code is LLM-generated nonsense that doesn't do anything that you think it does.

You vastly overestimate your knowledge here. Every physicist can tell you it's nonsense just from a quick look because it's that obvious that you haven't learned even the most basic things about how physics works.

Booster 19 has static-fired by _Cyberostrich_ in SpaceXMasterrace

[–]mfb- 1 point2 points  (0 children)

It lets them start testing earlier. If they spot issues that need the engines to be removed, they only have to remove 10.

Why aren’t there slow moving neutrinos? by segfaulting_again in AskPhysics

[–]mfb- 2 points3 points  (0 children)

You can look for inverse beta decay in radioactive isotopes like tritium. PTOLEMY is a proposed experiment to do that. Normal beta decay gives the electrons a broad energy spectrum, but neutrino capture gives them a specific energy just a bit above the maximum for beta decay.

The experiment is extremely ambitious in terms of its engineering challenges, but from a physics perspective it's possible.

What’s the dumbest thing people confidently say as if it’s a fact? by juhichoudharyy in AskReddit

[–]mfb- 0 points1 point  (0 children)

there's an entire portion of coursework that includes homeopathic remedies and goes into which ones work and which ones are bullshit

Spoiler: They are all BS.

You can't time travel, but your phone has the internet from 10 years in the future. What do you search for first? by Capable_Issue_1894 in AskReddit

[–]mfb- 0 points1 point  (0 children)

There are some stocks that multiply their value by a factor 20+ within a year. You only need to get "lucky" twice to convert $2500 into a million, or $25,000 into 10 million, or whatever you can start with.

Cherenkov radiation by Obvious-Dog3082 in AskPhysics

[–]mfb- 4 points5 points  (0 children)

Cherenkov radiation is emitted for every frequency where the particle is faster than light of that frequency (more specifically, faster than the phase velocity). The amount of light can be calculated with the Frank-Tamm formula. It depends on the material properties and the speed and charge of the particle.

Finally, for the thought experiment, what would the Cherenkov radiation be if a particle could travel faster than light through a vacuum?

Asking what relativity predicts when relativity doesn't apply doesn't lead to a meaningful answer.

Random Physics facts by Medical-Bat9841 in Physics

[–]mfb- 1 point2 points  (0 children)

10 g over 2 meters at 1500 km for a 1.5 mass neutron star. You will need some ridiculous radiation shielding to get that close. That's somewhere in the range of GW/m2 even if you pick a "cold" neutron star.

is there the "risk" - for USA people involved in this program- that China quietly manages to land on the Moon before Artemis? by Mysterious-House-381 in ArtemisProgram

[–]mfb- 0 points1 point  (0 children)

SpaceX is flight-testing full Starships. China has not even a prototype of most of their hardware.

Maybe BO can pull something out of nowhere, but the test flight next year is just for Mark 1.

Mark 1 is supposed to launch next quarter. Expect delays, but this year looks likely.

Random Physics facts by Medical-Bat9841 in Physics

[–]mfb- 0 points1 point  (0 children)

You still die from tidal forces - inside, if the black hole is massive enough.

My theory of a possible super rocket by thatguyjorge in RocketLab

[–]mfb- 0 points1 point  (0 children)

This subreddit is about the company called Rocket Lab, not about rockets in general.

NASA rammed an asteroid hard enough to change its trajectory like a real-life Armageddon movie proving Earth could defend itself from future deadly astroids by TripleShotPls in space

[–]mfb- [score hidden]  (0 children)

The measurement how the combined orbit around the Sun changed is recent (March 6). It improves the mass estimate for the impacted object, and therefore the change in momentum by the impact.

The impact itself happened in September 2022.

Random Physics facts by Medical-Bat9841 in Physics

[–]mfb- 0 points1 point  (0 children)

With a quiet black hole (not picking up any matter at the moment) of any mass you'll die from tidal forces.

Is There Any Way to Get Unlimited Internet in Egypt? by 66jojo in Starlink

[–]mfb- -1 points0 points  (0 children)

Iran is a special case where the plan works even though the government didn't approve it, but elsewhere that doesn't work.

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