Gregory's Server@johncarlosbaez let me be the second “Wow!”
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19 comments
@johncarlosbaez Numbers on this scale break my brain. Is that last sentence saying, basically, 38 seconds after the creation of the universe?   @Archnemysis @Archnemysis  @TerryHancock Looks like it's about 200,000X the Planck time -- which is "the smallest interval of time there can be", more or less.  @TerryHancock - very much "more or less", since nobody knows what the hell is going on at such short time scales. But still, the Planck time is a good unit to measure times when you're talking about gravitational waves produced by the Big Bang!  I'm a little rusty on my scientific notation, but i think it's 0.000000000000000000000000000000000000001 seconds. @Archnemysis - Not 38 seconds, 10⁻³⁸ seconds. As others have said in different ways, that means the gravitational background radiation was released about 0.0000000000000000000000000000000000000001 seconds after the Big Bang! Check out my timeline of the very early history of the Universe to put this in context: "..may fly within 10 years" Sigh, that hurts a bit. I recently spoke with some frustrated mission planners at ESA. It appears that juggling budgets, 22 member states and the scientific community seems to be quite the thankless job. @gnarf - it's a very tough job. But the spacecraft do eventually fly... some of them, at least. @johncarlosbaez well, the “or so” seems to have undergone some inflation, but glad to see we’re getting there!   @johncarlosbaez @CascadeTommy now I understand, so the gold cube is inside in a vacuum so that it does not get pushed around? And the outside is steered to keep it in the middle. Just hope it does not touch the sides! |
@CascadeTommy - I've been amazed by this experiment ever since I heard about it. Back in 1999 I wrote this:
"The idea is to orbit 3 satellites in an equilateral triangle with sides 5 million kilometers long, and constantly measure the distance between them to an accuracy of a tenth of an angstrom - 10⁻¹¹ meters - using laser interferometry. The big distances would make it possible to detect gravitational waves with frequencies of .0001 to .1 hertz, much lower than the frequencies for which the ground-based detectors are optimized. The plan involves a really cool technical trick to keep the satellites from being pushed around by solar wind and the like: each satellite will have a free-falling metal cube floating inside it, and if the satellite gets pushed to one side relative to this mass, sensors will detect this and thrusters will push the satellite back on course.
I don't think LISA has been funded yet, but if all goes well, it may fly within 10 years or so. Eventually, a project called LISA 2 might be sensitive enough to detect gravitational waves left over from the early universe - the gravitational analogue of the cosmic microwave background radiation!
The microwave background radiation tells us about the universe when it was roughly 10⁵ years old, since that's when things cooled down enough for most of the hydrogen to stop being ionized, making it transparent to electromagnetic radiation. In physics jargon, that's when electromagnetic radiation "decoupled". But the gravitational background radiation would tell us about the universe when it was roughly 10⁻³⁸ seconds old, since that's when gravitational radiation decoupled."
https://math.ucr.edu/home/baez/week143.html
@CascadeTommy - I've been amazed by this experiment ever since I heard about it. Back in 1999 I wrote this:
"The idea is to orbit 3 satellites in an equilateral triangle with sides 5 million kilometers long, and constantly measure the distance between them to an accuracy of a tenth of an angstrom - 10⁻¹¹ meters - using laser interferometry. The big distances would make it possible to detect gravitational waves with frequencies of .0001 to .1 hertz, much lower than the frequencies for which the ground-based...