Hot air is less dense than cold air. Could a hot-air balloonbe flown on the Moon, where there is no atmosphere?(a) No, there is no cold air to displace, so no buoyancyforce would exist.(b) Yes, warm air always rises, especially in a weakgravitational field like that of the Moon.(c) Yes, but the balloon would have to be filled withhelium instead of hot air
Stellar evolution
We may see thousands of stars in the dark sky. Our universe consists of billions of stars. Stars may appear tiny to us but they are huge balls of gasses. Sun is a star of average size. Some stars are even a thousand times larger than the sun. The stars do not exist forever they have a certain lifetime. The life span of the sun is about 10 billion years. The star undergoes various changes during its lifetime, this process is called stellar evolution. The structure of the sun-like star is shown below.
Red Shift
It is an astronomical phenomenon. In this phenomenon, increase in wavelength with corresponding decrease in photon energy and frequency of radiation of light. It is the displacement of spectrum of any kind of astronomical object to the longer wavelengths (red) side.
Hot air is less dense than cold air. Could a hot-air balloon
be flown on the Moon, where there is no atmosphere?
(a) No, there is no cold air to displace, so no buoyancy
force would exist.
(b) Yes, warm air always rises, especially in a weak
gravitational field like that of the Moon.
(c) Yes, but the balloon would have to be filled with
helium instead of hot air
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