What is nuclear fusion?

The splitting of a heavy atomic nucleus into two lighter ones, releasing energy The collision of hydrogen atoms that creates a chemical explosion The joining together of light atomic nuclei to form a heavier nucleus, releasing energy The burning of hydrogen gas in a very high-temperature flame

What is produced when the Sun fuses hydrogen nuclei in its core?

Carbon dioxide and water vapor Helium nuclei, energy (photons and neutrinos), and positrons Heavy elements like iron and gold Oxygen and nitrogen gas

What does Einstein's equation E=mc squared tell us about mass and energy?

Energy equals mass times the speed of light — not squared Mass is always conserved — energy and mass are completely separate Mass and energy are equivalent — a tiny amount of mass can be converted into an enormous amount of energy The equation only applies at the speed of light and is not relevant to everyday stars

The Sun converts about 600 million tonnes of hydrogen into helium every second. Yet the Sun has hardly changed over billions of years. Why?

The hydrogen is recycled by the corona back into the core The Sun actually burns very slowly — 600 million tonnes is a misprint The Sun contains an enormous amount of hydrogen — about 2 x 10 to the power of 30 kg — so it has enough fuel to last billions of years more New hydrogen is constantly added to the Sun from the solar wind

Of the 600 million tonnes of hydrogen the Sun fuses per second, how much becomes pure energy?

All 600 million tonnes — hydrogen is completely converted to energy About 4 million tonnes — the rest becomes helium About 300 million tonnes — exactly half is converted to energy Only a few kilograms — the rest is recycled

What prevents the Sun from collapsing under its own gravity?

The Sun spins fast enough that centrifugal force keeps it from collapsing The Sun's magnetic field creates a rigid structure that resists compression The outward radiation pressure from nuclear fusion balances the inward pull of gravity — called hydrostatic equilibrium The solar wind pushes back against the corona preventing collapse

Why does nuclear fusion require such extreme temperatures and pressures to occur?

Fusion only occurs in zero gravity — the Sun's weightless core is the key factor Fusion requires a catalyst like a black hole to start the reaction Protons are both positively charged and repel each other — they must be moving extremely fast (high temperature) and packed tightly (high pressure) to get close enough to fuse The high temperature is needed to vaporize the hydrogen — fusion only works with hydrogen gas

Nuclear fusion in the Sun produces neutrinos. Why were solar neutrinos a mystery to scientists for decades?

Neutrinos travel faster than light, so they arrived before scientists expected them Detectors on Earth were finding only about one-third as many neutrinos as fusion theory predicted — the missing neutrinos were eventually explained by neutrino oscillation No neutrinos were ever detected from the Sun — they do not exist Neutrinos were absorbed by Earth's atmosphere before reaching detectors

Why is nuclear fusion considered a potential clean energy source for Earth?

It uses the same fuel as coal plants but burns it more efficiently Fusion uses hydrogen (abundant in seawater), produces helium (non-toxic), and generates no long-lived radioactive waste Fusion reactors run on sunlight, making them renewable It is already powering cities in France and Japan

How does the proton-proton chain in the Sun differ from the nuclear fission used in today's nuclear power plants?

They are the same process — the Sun is just much larger Fusion joins light nuclei together; fission splits heavy nuclei apart — the Sun uses fusion while power plants use fission Fission joins light nuclei and fusion splits heavy ones The Sun uses chemical combustion, while power plants use nuclear reactions