"Speed of Light"

[Scott DeWar]

lets see, 100 trillion.
100,000,000,000,000

still 10 ^4 to go.

 

[Umbran]

Over so much time*, all the baryonic matter will decay to nothing.

The end of normal matter is, I think, currently estimated at 10^30 years. The end of black holes at 10^100 years.

 

[Scott DeWar]

I am normally not this anal, but . . . . .

10,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000

ok, 100 trill. uses 12 '0's so 10 trillion^ 8.5 power, i think
or maybe
[1 bill ^ 11] * 10 = 100 billion billion times 10? this one might be wrong.

 

[freyar]

The rate of expansion (often, the Hubble Parameter) is only recently known to any decent accuracy. (To about 2% is what I'm seeing, say, around 71-73. Previously, values between 50-80 seemed usual.)

I'm always kind of amazed we can make this kind of measurement at all. The various methods used are really ingenious.

That seems to show acceleration starting some time in the past, and increasing since then.

Given the uncertainties in the measurements, telling the rate of acceleration seems unlikely.

Yes, for most of the life of the universe, the expansion was slowing down, as you'd expect from gravity pulling things together. The positive acceleration (speeding up) has only
kicked in recently (the last billion years or so, if I recall correctly). It's basically an issue of scales, meaning that the "dark energy" has just recently become of the same density as normal matter.

The basic implication is that a computation of the age of the universe cannot rely on a constant Hubble parameter values.

One measure of the age of the universe is telling the amount the background radiation is red-shifted: That shift basically integrates the effect of expansion over time. Then, knowing the rate of expansion, and inverting the integration, the age can be obtained.

An increasing Hubble parameter will make for the same shift over a smaller amount of time. Not sure quantitatively how much that would be, but I'm guessing on the order of 10%, or a small multiple thereof, for the measured acceleration, and not of the order of 100% or more. But, I could be very off on that estimate, and the estimate is very probably thrown off anyways by the basic uncertainty of the current parameter value.

That's right. With a constant Hubble parameter, you can just extrapolate back linearly: age of universe = 1/H_0 in appropriate units. Acceleration makes H_0 (the value of the Hubble parameter now) bigger than it "should" be, so the simple estimate of the age of the universe isn't old enough. And the correction is not quite 10%.

 

[Mustrum_Ridcully]

Over so much time*, all the baryonic matter will decay to nothing.

There would just be the occasional flash of black holes evaporating.

Such a dark and gloomy place.

Thx!

*100 trillion years might not be long enough. At least for black hole evaporation, I think we are up in the 10^100 years range

Of course, that may be nothing compared to the scenario of the Big Rip, where the acceleration of expansion is so fast that at some point, even atoms get torn apart... But it seems with our current understanding, the expansion won't get that bad.



I wonder if there could be some new types of patterns emerging on that scale?

 

[Umbran]

Of course, that may be nothing compared to the scenario of the Big Rip, where the acceleration of expansion is so fast that at some point, even atoms get torn apart... But it seems with our current understanding, the expansion won't get that bad.

It isn't quite about "how bad the expansion gets". It is about how much pressure "dark energy" gives for its density (via the ratio of those things). Essentially, it is about the strength of the "force" that causes expansion. If it is strong enough, it'll eventually overcome gravity, the electromagnetic, and nuclear forces, and matter will just sort of dissolve away.

At the moment, the experimental errors are large enough that we can't tell for sure which state we are in - looking at a Big Rip or not.

I wonder if there could be some new types of patterns emerging on that scale?

Patterns... of what? And what is "that scale"?

 

[Mustrum_Ridcully]

Patterns... of what? And what is "that scale"?

Imagine those left-over black holes that slowly evaporate forming a pattern. I figure that most of these would be galactic black holes, so the scale would be grand. Theoretically, a group of black holes clusted around another black hole might evaporate so much energy in the direction of the center black hole that it grows instead of shrinks for a while. I wonder if there could be something creating a pattern, some form of replication possible that we haven't considered yet... I don't currently know anything particular that could come, mostly it seems that, if such black hole "clusters" that can feed a central black hole where to exist, it would just mean that the center black hole last a bit longer, nothing more fancy.