Search results
Results from the WOW.Com Content Network
For example, galaxies that are farther than the Hubble radius, approximately 4.5 gigaparsecs or 14.7 billion light-years, away from us have a recession speed that is faster than the speed of light. Visibility of these objects depends on the exact expansion history of the universe.
For supernovae at redshift less than around 0.1, or light travel time less than 10 percent of the age of the universe, this gives a nearly linear distance–redshift relation due to Hubble's law. At larger distances, since the expansion rate of the universe has changed over time, the distance-redshift relation deviates from linearity, and this ...
Therefore, it is not remarkable that according to Hubble's law, galaxies farther than the Hubble distance recede faster than the speed of light. Such recession speeds do not correspond to faster-than-light travel. Many popular accounts attribute the cosmological redshift to the expansion of space.
A cosmological horizon is a measure of the distance from which one could possibly retrieve information. [1] This observable constraint is due to various properties of general relativity, the expanding universe, and the physics of Big Bang cosmology. Cosmological horizons set the size and scale of the observable universe. This article explains a ...
is the object's velocity or the sound speed in the surrounding medium if < R {\displaystyle R} is the Bondi radius, defined as 2 G M / c s 2 {\displaystyle 2GM/c_{s}^{2}} . The Bondi radius comes from setting escape velocity equal to the sound speed and solving for radius.
That system failed in space during the final phase of Ariane 6's otherwise successful debut launch in July, adding to the global rocket industry's long list of pressurization challenges ...
Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level , this speed is approximately 343.2 m/s (1,126 ft/s; 768 mph; 667.1 kn; 1,236 km/h).
In space, no one can hear you scream -- but you may hear a knock. When he was alone in a spacecraft in 2003, astronaut Yang Liwei reportedly heard a "knock" despite being alone.