Editing 2186: Dark Matter
Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.
The edit can be undone.
Please check the comparison below to verify that this is what you want to do, and then save the changes below to finish undoing the edit.
Latest revision | Your text | ||
Line 8: | Line 8: | ||
==Explanation== | ==Explanation== | ||
− | [[Megan]] and [[Cueball]] are talking about {{w|dark matter}} | + | {{incomplete|Created by a DARK MATTER SQUIRREL ON A SPINNING BIRD FEEDER. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}} |
+ | In this comic, [[Megan]] and [[Cueball]] are talking about {{w|dark matter}}. Megan states that dark matter's density across the solar system is 0.3 GeV/cm<sup>3</sup>. Since Cueball likely does not have a science background, he does not understand what this means, so, to clarify, Megan explains that 0.3 GeV/cm<sup>3</sup> equates to one squirrel's worth of dark matter for the volume of the Earth. For the last two panels, Cueball conflates this with dark matter actually ''being'' a squirrel for comedic effect, enraging Megan. | ||
− | The {{w|gigaelectronvolt}} (GeV) is a unit of energy that can be converted to a mass using {{w|Mass%E2%80%93energy_equivalence|Einstein's formula}} ''E'' = ''mc''<sup>2</sup>. It is typically used for subatomic particles, such as {{w|weakly interacting massive particles}} (WIMPs), one of | + | The {{w|gigaelectronvolt}} (GeV) is a unit of energy that can be converted to a mass using {{w|Mass%E2%80%93energy_equivalence|Einstein's formula}} ''E'' = ''mc''<sup>2</sup>. It is typically used for subatomic particles, such as {{w|weakly interacting massive particles}} (WIMPs), one of several contending possibilities on the still-open question of the composition of sark matter, and the one which Megan's uniform density figure assumes constitutes most of it. For example, the mass of a proton is 0.938 GeV/''c''<sup>2</sup>. However it is frequent to omit the ''c''<sup>2</sup> factor and to represent masses in GeV (or MeV). A mass represented as 0.3 GeV is equal to 5.35 × 10<sup>−25</sup> grams [https://www.wolframalpha.com/input/?i=0.3+(GeV%2Fc%5E2)+in+grams]. |
− | + | This implies a {{w|squirrel}} has a mass of 580 g [https://www.wolframalpha.com/input/?i=(0.3+(GeV%2Fc%5E2)%2Fcm%5E3)+*+(volume+of+earth)+in+grams] (about 1.3 lb), which is a typical mass among several species of common squirrels. | |
− | + | Here is a reference to a paper that comes up with the dark-matter density of 0.3 GeV/cm<sup>3</sup>: [https://arxiv.org/abs/1205.4033 On the local dark matter density]. | |
− | + | The title text imagines using a spinning bird feeder like a {{w|particle accelerator}}, colliding hydrogen atoms at relativistic speeds to detect new and exciting particles like the {{w|Higgs boson}}. Note, however, that accelerating even [https://what-if.xkcd.com/1/ one squirrel] to relativistic velocities would destroy the feeder and be deadly to any birds near the feeder (not to mention the squirrel). | |
+ | |||
+ | [[:Category:Squirrels|Squirrels]] are a recurring topic on xkcd, but are not a serious alternative to WIMPs as a scientific explanation for the composition of dark matter. Since the September 2015 detection by the {{w|LIGO|Laser Interferometer Gravitational-Wave Observatory}} (LIGO) and subsequent confirmation by the {{w|Virgo interferometer}} of gravitational waves from an unexpectedly large number of merging {{w|black hole|black holes}} larger than those produced by stellar collapse, {{w|primordial black holes}} have become a popular alternative explanation to WIMPs (and squirrels), attracting [https://arxiv.org/abs/1605.04023 proponents at NASA,] and [http://www.buchaltercosmologyprize.org/#announcements other cosmologists] for [https://arxiv.org/abs/1711.10458 a number of reasons]. However, primordial black holes as dark matter remain controversial, because their existence as such [https://iopscience.iop.org/article/10.1088/2041-8205/720/1/L67 would exclude alternative explanations.] | ||
==Transcript== | ==Transcript== | ||
Line 40: | Line 43: | ||
[[Category:Comics featuring Cueball]] | [[Category:Comics featuring Cueball]] | ||
[[Category:Squirrels]] | [[Category:Squirrels]] | ||
− | [[Category: | + | [[Category:Astronomy]] |
[[Category:Physics]] | [[Category:Physics]] |