If I were in a place with no other gravitational force how long before I would collapse into a star?

[PlainJain]

@engineer_comp_geek

Small objects, like you, don’t even have enough mass to squish themselves together into a sphere.

Disclaimer: I’m waaay out of my depth here.

Anyway, is that really true? Given enough time wouldn’t the atoms decay to the point where gravity would be the stronger force?

[Chronos]

So far as we know, aside from the rare odd carbon-14 or the like (there aren’t enough of them to matter), the atoms that make up a human body never decay. The molecules, though, can, through the processes that we usually think of as “rot”, and if you let that go long enough, you’ll eventually liquify. Once you’ve liquified, then yes, you would puddle into a sphere.

[Half_Man_Half_Wit]

@Chronos

The Pauli Exclusion Principle can’t itself actually generate a force. It’s true that two fermions can’t occupy the same state simultaneously, but how close two can be before it’s the same state depends on the forces between them. Hence, ultimately, degeneracy pressure is a manifestation of one of the familiar fundamental forces: In a white dwarf, it’s the electromagnetic force, and in a neutron star, it’s the strong nuclear force.

I’m not sure I understand you correctly, but I don’t think that’s right: even a free (i.e. non-interacting) Fermi gas exhibits degeneracy pressure, simply due to the fact that only two particles of opposite spin can occupy a phase space cell of size (Δx)[sup]3/sup[sup]3[/sup] ~ ħ[sup]3[/sup]; so if you’ve got a total volume V, then on average a particle will be localized to about Δx = (V/2n)[sup]1/3[/sup] if you’ve got n particles, which gives a momentum uncertainty of about Δp ~ ħ(2n/V)[sup]1/3[/sup]; so the smaller you make the box, the higher the average momentum, and thus, pressure resisting any further shrinkage. This is the reason even free Fermi gases don’t condense the way bosons do (although some interacting ones do).

[Leo_Bloom]

::“Shrinkage?!?”::

Carry on.

[Exapno_Mapcase]

@Chronos

So far as we know, aside from the rare odd carbon-14 or the like (there aren’t enough of them to matter), the atoms that make up a human body never decay.

There are several decay isotopes in the typical human body.

Q How much 40K and 14C are in the typical human body?

A Potassium-40 content of the body can be obtained from its natural abundance of 0.0117 percent of potassium and calculating the specific activity of natural potassium (30.5 Bq g-1) using the half-life (1.28 x 109 y). The potassium content of the body is 0.2 percent, so for a 70-kg person, the amount of 40K will be about 4.26 kBq. Carbon-14 content of the body is based on the fact that one 14C atom exists in nature for every 1,000,000,000,000 12C atoms in living material. Using a half-life of 5,730 y, one obtains a specific activity of 0.19 Bq g-1 of carbon. As carbon is 23 percent of the body weight, the body content of 14C for a 70-kg person would be about 3.08 kBq.

Q How much 210Po and 210Pb is in the typical human body?

A According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 1982 Report, “Ionizing Radiation: Sources and Biological Effects,” 70 percent of the body content of 210Pb is in the skeleton. The UNSCEAR report estimates the typical 210Pb concentration in the skeleton to be 3 Bq kg-1, which equates to a total skeletal activity of 15 Bq for a 70-kg man. The other 30 percent of the 210Pb in the body, 6.4 Bq, would be distributed more or less uniformly throughout the soft tissues. The grand total of 210Pb in the body is thus 21.4 Bq.

The UNSCEAR report assumes the 210Po concentration in the skeleton to be 80 percent that of the 210Pb concentration. The UNSCEAR report estimates that the soft tissue concentration of 210Po is 2.4 Bq kg-1, which translates to a total skeletal 210Po activity of 12 Bq for a 70-kg man. In the soft tissues, the UNSCEAR report assumes a one-to-one ratio between 210Po and 210Pb. Hence the 210Po activity in the soft tissues would be 6.4 Bq. The grand total of 210Po in the body would be 18.4 Bq.

Levels of 210Po and 210Pb are expected to be lower for women than men and lower for children than adults. Smokers have higher concentrations than nonsmokers.

[Half_Man_Half_Wit]

@Leo_Bloom

::“Shrinkage?!?”::

It’s, uh, a technical term…?

[Chronos]

Quoth Exapno:

There are several decay isotopes in the typical human body.

Yeah, that’s why I said “and the like”. It’s not just C14, but all of the unstable isotopes combined are still a very small portion of the body. The stable atoms are by far enough to maintain the body in a body-shaped solid structure.