Theresa May will still be clinging-on as Prime Minister and still not have got Brexit over the line by then ?
When a star dies, destroying so much around it, it’s the small, dense rocky planets that are the objects most likely to be left standing while the heavy, gassy planets crumble and perish. A team of astrophysicists came to this conclusion after modeling the tidal interactions between a white dwarf star and a nearby planet to …
Tangentially relevant to the nuke thing: although we know that the Sun is too small to be a candidate for a future supernova, if it wasn't there's an interesting question:
which is brighter: a supernova seen from the distance we are from the Sun, or an exploding hydrogen bomb pressed against your eyeball?
The supernova is brighter, by nine orders of magnitude. Inevitably this comes from what-if.xkcd.com. Supernovae are just fucking silly.
Sadly only one upvote to give you. As I've just read the xkcd link you provided, and it's even more cool and interesting than that.
Sure it's amazing how bright that supernova is.
But he's using it as an illustration of how stupidly amazing supernovae are. In that you can get an instantly lethal does of neutrino radiation out to about the orbit of Mars.
So assuming that you built a bunker in the centre of Mars, with really good air conditioning and survived the expansion of the star, the absurdly stupidly ludicrously huge numbers in the neutrino burst would simply wander through the planet, as neutrinos do, and kill you anyway. That's a lot of neutrinos. Given our detectors at the bottom of mines pick them up in ones, out of the zillions passing through the Earth all the time.
Supernovae are really cool, but you wouldn't want one to go off in your back garden. There is actually one visible in 8" scopes in NGC 5353 at the moment, a comfortable 110 million light years away. It is the 14th one I have managed to see. Odd to think that when this last one went off dinosaurs were roaming the earth
don't worry, some wackos will claim it's human activity causing the sun to die, and come up with charts and graphs and modeling and legislation to curb our personal freedoms and screw us up economically in order to "solve" it.... and accuse EVERYONE who doesn't buy into this nonsense of being "deniers"...
(troll icon, naturally)
The Sun's luminosity and surface temperature are increasing by about 10% every billion years, so in a couple of billion years time, the Earth's surface will be too hot to sustain liquid water. Game over. And in five billion years, when the Sun runs out of hydrogen and turns into a red giant, there's an even chance that it will swallow the Earth as it expands. Mercury and Venus are definitely doomed to this fate, and the Earth may also end up inside the Sun.
But on a truly astronomical timescale, on the order of 10**38 years, all baryonic matter will vanish as protons decay into muons and electrons. Then we're *really* stuffed. (Reference: "A Dying Universe", F.C. Adams and G. Laughlin, 1997, Reviews of Modern Physics, Vol. 69, pp 337-372)
you sure about mercury leaving orbit? I would expect it to crash into the sun before that would happen... due to very slow orbital decay from solar wind, if for no other reason.
so that's something to ponder I guess, if mercury's orbit is affected more by constant mass loss from the sun [energy from fusion as well as solar wind], or by the solar wind itself creating friction and orbital decay.
As mass of the sun goes down, mercury's escape velocity would ALSO go down, but very very slowly. Similarly, the slow orbital decay. Maybe they balance each other out?
Answers own question:
Existence of collisional trajectories of Mercury, Mars and Venus with the Earth
Laskar, J. & Gastineau, M. (2009)
Nature, 459, pages 817–819 (11 June 2009)
Jacques Laskar is the real thing when it comes to Solar System dynamics. This paper reports numerical simulations of the orbits of the planets over 5 billion years. In around 1% of them, the eccentricity of Mercury's orbit is pumped up by secular resonances, leading to scenarios where it plunges into the Sun or collides with Venus. In one scenario, the orbits of all four inner planets are de-stabilised, with catastrophic consequences.
Don't have nightmares :-)
I think this a bit academic. The image it's self show's a solar system exploding outward.
Red Giant sweeping along the inner planets and so cooking the rocky bits to a crisp but intact
As fissionable material dwindles the sun will collapse sending out a shock wave (OK we're saved, whoops)
The much loved book Isaac Asimov collapsing universe before I'd even heard of Stephen Hawking as my mantra
The alternative version is:-
The world will end a week next Tuesday.
Note to Siti 3000 BCE before the written word who would have considered communication through radio waves?
So what that means from an Existential philosophical perspective is that no-one gets out of here alive? No one. At any point. Anywhere. Which then makes the meaning of life (not that I actually believe there is one) to be to stop worrying and just enjoy the time while we are here, because as Proximo said to Maximus... "ultimately we're all dead men".
Which in turn means that the philosophy of Bill S Preston Esq. and Theodore "Ted" Logan were right all along. Whoah!!!!
I fail to see where tidal forces come in. The sun will have substantially the same mass, through time, and gravity is a function of mass (and distance) neither of which stand to change. Strictly, gravitational force is the attraction between two (or more) bodies, or the constituents of one body. So, nothing changes substantially, in a gravitational sense, as the sun dies, to the orbiting bodies
Not so. The orbiting bodies raise tides on the central body. Energy and angular momentum are exchanged. The orbits change. This is why the Moon is slowly drifting away from the Earth and the Earth's rate of rotation is decreasing. That in turn leads to the need for leap seconds, and hey presto, it becomes an IT problem :-)
The force of gravity grows stronger, the closer you approach a massive object such a a star or gas giant like Jupiter. Now consider a planet or moon orbiting such a massive central body. There's a critical distance, known as the Roche Limit, where the difference between the force of gravity on the star/planet-facing side is so much greater than the force of gravity on the side furthest from the star/planet that it tears the orbiting body apart. This is a likely scenario for how Saturn's rings were formed: a small satellite's orbit took it so close to Saturn that the differential gravitational forces ripped it apart. It's also the fate that awaits Phobos and Deimos, the moons of Mars, which are slowly spiralling in towards the planet.
The distribution of the gradient does change.
See below. Consider a black hole of 3 sun masses, and a red giant of 3 sun masses. The Roche Limit, of each would be different (AFAIK, I've not googled the math to check it, sorry, I'm a layman! :P ).
PS, it seems that "R" radius of the larger body (Sun in our case) is influential in the variable of the Roche Limit. :)
I guess this is because each position in the volume of the star/planet will also have a gravitational gradient caused by the surrounding material (if it's the size of a planet, it's a lot of rock! and you can be gravitationally pulled in any direction the material is, just less on your side with less material ). Imagine falling through a planet or star, you would feel gravity pulling in both directions as you pass the center, but still get some gravity on both directions until you reach a surface where all the gravity would then be in one direction (as the whole star/planet would be on one side of you).
So the gradient in gravity will effect how strong a "slope" and difference is exerted on the second/smaller body.
You're misreading that Wikipedia article. Yes, R_M appears in one of their equations, but only because that's the one that compares their densities, rather than their masses directly. In the case we're considering here, the density and radius are changing, but the mass is staying relatively constant. Radius of the Sun doesn't enter into it. The only situation where it's relevant to the gravity field when comparing spherical bodies is when you'd be within one of them.
ETA: See also Wikipedia on the shell theorem, https://en.wikipedia.org/wiki/Shell_theorem . It's pretty much what you were saying in your penultimate paragraph.
I also missed that due to GR you don't feel gravity "pulling" in both directions... (as gravity/acceleration is all you feel and cannot distinguish between it).
I'm still trying to understand how distributing the mass over a greater space does not change the shape of the gravitational field the earth would be in. We are talking about inflating the sun to the size of our current orbit here! (As you say, when R becomes large enough to overtake the earth).
Though I will concede if I can figure out/be shown how the math/field/etc does not change shape/concentration as the size of the sun increases or decreases.
Just have a look at the WP article on Shell theorem mentioned above by KarMann, the math is detailed there. It demonstrates how the gravity field outside an homogeneous spherical body is the same as if all the mass was concentrated at the center of the body. It derives that the gravity only depends on the mass of the body, not its size, however close you may be to its surface.
What are the probabilities of ... moving in with a nice younger model?
For people over 30, the chance of that is inversely proportional to money/age2. Where money is in millions of dollars. The full formula is:
1 - money/(age2)
e.g. have $1billion and are 40 years old:
= 1 - (1b/1m)/(402)
= 1 - 1000/1600
= 1 - 0.625
if you have $1billion and are 90 years old:
= 1 - (1b/1m)/(902)
= 1 - 1000/8100
= 1 - 0.123
Given that our Sun is 99.8% of *all* the mass in our solar system; If we can extract elements heavier than Hydrogen, we have all the building materials we need and we can then feed the hydrogen back into the sun extending it's life!
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