# Would dark energy save the earth for a while as the sun heats up?

Would the expansion of space (e.g. dark energy) move the earth further away from the sun over time, possibly saving us for perhaps a few billion years as the sun heats up?

Scientists now tend to think that the sun is heating up very gradually (e.g. over billions of years): http://tvblogs.nationalgeographic.com/2010/07/21/hotter-and-hotter/

Dark energy is the unexplained accelerating expansion of the universe, as described here: http://en.wikipedia.org/wiki/Dark_energy

Put another way, my question is, is dark energy working at such a rate that it would move earth (and other planets) further from the sun and prolong life on earth as the sun heats up?

• Unfortunately not. Dark energy act only on very large scales, i.e. between galaxies sufficiently far apart. On smaller scales, i.e. local galaxies, inside the galaxies, solar systems, and planets, gravity dominates and keeps objects bound. – pela Apr 29 '15 at 19:51
• A similar question was asked here - much more scientific answer than the one I gave below if interested: astronomy.stackexchange.com/questions/7967/… – userLTK Apr 30 '15 at 1:40

I don't think this is a bad question, and I think Pela is essentially correct, the effect is very small.

Dark energy doesn't expand objects, for example, cause those are bound together, but dark energy should expand space between the sun and the earth though the effect is tiny.

If we take this number, 68 KM per second per 1 million light years (link below), that's 245,000 KM per hour per million light years or about 1 KM every 4 hours per lightyear. With 63,000 Astronomical units per light year, between the sun and the earth, we can expect the earth (assuming it's in a perfectly stable orbit around the sun - which it's not, but lets say it is), a velocity of 1KM/30 years. And that's over the age of the universe. The earth/sun is only 1/3rd the age of the universe, so dark energy has accelerated the earth maybe 1 KM/90 years velocity since the formation of the solar system. That's a pretty small push. A velocity change of a bit a meter per year over the age of the solar-system. The effect of the solar wind and the Jupiter and Venus orbital tugging are probably greater than that.

Now, over a few billion years, a small velocity change of 1 meter per year would add up - so I think dark energy is part of the solar system's long term orbital calculation. I might be wrong on that, but I think it has a measurable effect over billions of years even in distances as small as planetary orbits.

But would it save the earth - I doubt it. The sun's heating up accelerates over time. It will at some point in the future, move too fast and get too hot for the earth, so, we'll have to save ourselves, either by moving the earth or terraforming mars, or building space colonies or some combination of all 3. The good news, we have tens of millions, maybe hundreds of millions of years to figure that stuff out.

Dark energy has been useful though. It's probably kept us from crashing into Andromeda and/or the great attractor - however far away that is. Certainly delayed those collisions (We're never going to crash into the great attractor, I gather, thanks to dark energy), and crashing into Andromeda, when it happens, might harmless anyway, but I'm just kind of thinking out-loud.

I do think it's a good question as there probably is some small expansion due to dark energy between the earth and the sun. If my numbers are wrong, I welcome correction.

• This answer is wrong. The figure of 68 km/s per million light years in the linked article is just the Hubble constant with the wrong units (it should be parsecs). The Hubble expansion has no local effect. The local effect of the dark energy is roughly that of matter with a uniform density of $-10^{-26}\text{ kg}/\text{m}^3$ (negative because it's repulsive). At 1 AU, this is roughly equivalent to decreasing the sun's mass by about 1 part in $10^{22}$. The effect of this change of mass is a tiny change in the parameters of earth's orbit, not an increase in distance over time. – benrg Sep 25 '20 at 0:01

I welcome further discussion, and evidence supporting, or refuting my answer.

If my idea is correct that antimatter is distributed fairly evenly through the voids between galaxies, and that antimatter is the cause of dark energy, then no, dark energy will not move earth out of the way of a sun that is heating up (e.g. it would have no effect, or very little effect). This is because antimatter would not exist within the solar system. Solar wind, and other particles would annihilate any antimatter that found its way into the solar system. A "galactic wind" would also likely prevent antimatter from even entering the galaxy.

It would be interesting to see if we can observe earth's past position in relation to the sun (e.g. perhaps by examining the rocks or fossils) and see if earth is migrating out further from the sun or not. This analysis may show us if dark energy is indeed "everywhere" (true if the earth used to be closer, and is migrating away from the sun) or just in the "voids" (true if the earth is not migrating away from the sun).

I very much welcome further discussion and answers. I especially welcome someone to perform the research as discussed in the prior paragraph.

• This is not correct. Antimatter are particles that have opposite properties (charge, etc.) from their "normal" counterparts. Their existence hase been observationally confirmed, mostly in labs, but also in Nature. This has nothing to do with dark energy, the existence of which has only been inferred indirectly and is still quite uncertain. Furthermore, dark energy only has an effect on much, much larger scales than the Solar system. – pela Apr 29 '15 at 19:48
• What is the basis for your idea that "antimatter is the cause of dark energy"? As for the Earth's distance from the Sun in the distant past, that's probably already been studied. I'd expect Earth to move into a slightly larger orbit as the Sun loses mass. It's also believed that the planets' orbits have changed substantially, especially in the very early history of the Solar System, and especially Jupiter. – Keith Thompson Apr 30 '15 at 1:05
• @KeithThompson I have an idea that while matter "absorbs" space / has gravity, that antimatter injects space (has negative gravity) – Jonathan May 1 '15 at 22:31
• Both matter and antimatter have positive mass, for what that's worth (I believe it's been experimentally verified). There might be such a thing as negative matter, that might have characteristics similar to what you describe, but I think it would be very different from antimatter, and I'm reasonably sure it hasn't been detected. Someone who knows physics better than I do might want to comment further. – Keith Thompson May 1 '15 at 23:04