Comments of the Week #131: from seeing the Big Bang to trillions and trillions [Starts With A Bang]

“There are in fact 100 billion galaxies, each of which contain something like a 100 billion stars. Think of how many stars, and planets, and kinds of life there may be in this vast and awesome universe.” -Carl Sagan

And at long last, Carl Sagan’s estimates are finally out of date. It’s not ~100 billion galaxies, but a number more like two trillion, and at last we know! If you wanted to know what the topic of this month’s Starts With A Bang podcast was going to be, there’s your answer! Look for it sometime over the next two weeks. Of course, none of that has changed what we write about here at Starts With A Bang! If you missed anything this past week, catch up now:

• How can we see all the way back to the Big Bang? (for Ask Ethan),
• Galaxies found close together show signs of impending doom (for Mostly Mute Monday),
• What’s so special about special relativity?,
• Where does our arrow of time come from?,
• How far away are the stars? Scientists still don’t know, and
• Hubble’s latest breakthrough reveals trillions of unknown galaxies in the Universe.

Also, I was on my local news channel again, talking about Hubble, Mars missions and — ever so briefly — my new upcoming book that I’m more than halfway through writing!

From Anonymous Coward on historical hurricanes: “The world ocean Panthalassa as it existed back in the Devonian seems like it was almost as big as the Atlantic and Pacific oceans put together, and I’d think a storm moving across such a huge expanse of warm water completely uninterrupted by land masses would gain strength like no storm possible today, until it hit the coast of Gondwana or Euramerica.”

It’s possible that storms would have had the potential to reach even greater strengths hundreds of millions of years ago than they do today. There are a few factors that contribute, including:

• increased air and ocean temperatures over today,
• longer oceanic tracts for the storms to traverse and gain strength over,
• and slightly larger wind speeds in general back then.

A.C. would like to focus on the second.

That’s actually the most difficult of the three things to predict. Take the hurricanes that strike the United States these days. Where do they form? Mostly in the Caribbean, most of the rest in the Atlantic, and only a few off the western coast of Africa. The last category is where the deadliest, strongest storms tend to originate, but for some reason very few storms, number-wise, form there. In addition, just because the conditions are met for “how hurricanes form” in general doesn’t mean that hurricanes are actually going to form where you want. For example, here’s where hurricanes are seen to actually occur on Earth today.

Although there’s a longer track for these storms to take in a world that has more contiguous, equatorial oceanic area, will that matter? It might, but as far as I know, it may not as well.

But warmer temperatures and faster Earth rotation back then should have resulted in stronger storms, even if all the other conditions were the same. But by how much? I don’t think anyone quite knows.

From Naked Bunny with a Whip on photons and the Big Bang: “One of the tricky aspects of discussing cosmology is getting past the idea that the universe is a sphere and that the Big Bang happened at the center of the sphere. If that were the case, then the CMB would have already zipped past us as we glide away from the center more slowly than light. But the large scale structure of the universe isn’t so intuitive, and that’s a big stumbling block that comes up all the time.”

From Carl on Maxwell’s demon: “This idea became known as Maxwell’s demon, and it enables you to decrease the energy of the system after all!”
Seems like it should be “entropy”, not “energy”.”

This was a typo. But to clarify, if you take a system of particles, their individual kinetic energies and the distribution of those energies determine the temperature of the system. In general, slow-moving particles with low kinetic energies represent “cold” systems and fast-moving ones with high kinetic energies represent “hot” systems. There is a connection between energy and entropy in that a hot system and a cold system, separately, can do work and can be converted into an engine, and hence is a low-entropy system. On the other hand, two systems with the same total energy but where both systems are the same, lukewarm temperature can do no work and will be a 0% efficient engine, and is therefore a high-entropy system.

Maxwell’s demon would allow you, by segregating the particles due to an external influence, to reverse the entropy of the system. Suddenly, the post-demon system would be able to do work, would be able to create a quite efficient engine and would have much lower entropy than the original equilibrium system. That’s the deal!

From Sinisa Lazarek on entropy and absolute zero: “If I have two baseballs, and one is hot and other cold. You are saying that the cold baseball has higher entropy then the hot one?! If you are tying it to thermals, shouldn’t it be the opposite? More heat, higher entropy… not more heat, lower entropy.. After all, at absolute 0, entropy is 0.”

No. I’m saying that in a system like the Universe — a huge, gigantic system — uniformly low energies are your enemy from an entropy perspective. The “cooled” Universe is at lower entropy than the hot Universe, but that’s also because it’s more expanded and clumpier, not just because it is cooler. At absolute zero, entropy is 0 for an ideal gas, not for all systems. But let’s go back to the baseballs, because that’s where the real interesting things lie. And I’m going to assume, for the purposes of this exercise, that the two baseballs are the only things going on in this Universe.

If both of those baseballs are hot, you can’t transfer any energy between them. You can’t set some third “test particle” up on one of them and cause it to do anything useful. From a work point of view, you’re out of luck. This is the same as if both of those baseballs are cold, or at absolute zero. In order to do work, you need a gradient. So what I’m saying, and I hope this is clearer, is that a lower entropy system has a heat source and a heat sink, or two reservoirs at different temperatures. A hot baseball and a cold baseball have lower entropy than two hot baseballs, if those “two baseball systems” are isolated systems. Does that make sense?

From Ciaran on very, very long baseline observations: “My first thought on seeing how messy that parallax data is why you’d only use one satellite.
Wouldn’t two on opposite sides of the earth’s orbit give you the full possible resolution of the telescope and take the proper motion out of the equation completely? Would that just be too expensive or is there another reason not to do that?”

From a practical point of view, what you’re asking for is some very high-quality telescopes at differing locations around Earth’s orbit. Because of how gravity works, there are only three locations that make sense if your goal is to create very long baselines with Earth: the L3, L4 and L5 Lagrange points.

There are no satellites, natural or artificial, around L3. It’s an unstable Lagrange point, and getting there is much harder than getting to L1 or L2, which are also unstable. Because we can see and communicate with L1 and L2, and they’re relatively close (a round-trip light signal is measured in seconds, rather than in half-hours), they’re much easier to deal with. L3 is a mess.

But L4 and L5 aren’t much better if precision is your goal. The only spacecraft we’ve ever sent there are NASA’s Stereo-A and Stereo-B. Neither one made it to the Lagrange point and stayed there; they simply drifted through. And Stereo-B has been plagued by mission failures. In other words, it’s a great idea, but we haven’t had the right technical achievements to make this doable just yet. Getting to Hipparcos was a big deal; getting to Gaia is an even bigger one. But neither of those were NASA projects; I suppose perhaps the next big deal would be getting NASA to care about this problem.

And finally, from Philip E Coleman on the trillions of galaxies in the Universe: “The never ending story that can never fully be explored”

Our knowledge of what’s out there will always be fundamentally limited. First by what we’re willing to invest, next by our technology, and finally, even if those two restrictions were removed, by the limited information the Universe provides us with. Even if we were able to collect every photon of every wavelength sent our way from every star, galaxy, nebula and more from now until the end of the Universe, the information we received would still be finite. There would still be mysteries the Universe didn’t provide us with enough information to solve.

The key, in the time we have with the Universe we have, is to learn as much as possible and understand as much as we can. It’s to ask the best questions and come as close as we can to answering them honestly and to the best of our abilities, while simultaneously being honest about the uncertainties and the unknowns. That is the great journey of science; that is the great journey of life.

Let’s go a little further, together, with each and every moment, story and week that passes. I’ll be here, and I hope you will, too.