# Tag Info

-8

UAPs got here somehow. So, about a month ago, the United States government has issued a report on Unidentified Aerial Phenomena (UAPs), which is basically the modern US government term for UFOs, stating that they're real, they're not American, they do things beyond our current understanding of physics, and they don't know what they are. The actual wording of ...

11

The density of the interstellar medium varies hugely, so the specific problem of Sol-to-Proxima-Centauri travel is different from the general problem of interstellar travel. According to WP: In cool, dense regions of the ISM, matter is primarily in molecular form, and reaches number densities of $10^6$ molecules per $cm^3$ (1 million molecules per $cm^3$). ...

8

Based on this answer: $$E \approx \frac{1}{2} m v^2 = \frac{1}{2} m c^2 \left(\frac{v}{c}\right)^2$$ The mass of a proton $m_P c^2$ is about 938 MeV, so if an innocent atom of hydrogen or bare proton in space were hit by a spacecraft at 0.1 c, in the spacecraft's frame it would look like a speedy proton. Of what energy? E = \frac{938}{2} 0.1^2 = 4.7 \text{ ...

Top 50 recent answers are included