At the latest, in about 5 billion years, stellar evolution predicts our sun will exhaust its core hydrogen and become a red giant. In doing so, it will become thousands of times more luminous. As a red giant, the Sun will lose roughly 30% of its mass, so, without tidal effects, the Earth will be in an orbit 1.7 AU (250,000,000 km) from the Sun when the star reaches it maximum radius. Therefore, the planet is thought to escape envelopment by the expanded Sun's sparse outer atmosphere, though most (if not all) existing life would have been destroyed by the Sun's proximity to Earth. However, a more recent simulation indicates that Earth's orbit will decay due to tidal effects and drag, causing it to enter the red giant Sun's atmosphere and be destroyed.The Earth will likely be dragged into the Sun when it becomes an enlarged red giant by no later than about 7.6 billion years; before actual collision with the sun, the oceans would evaporate, and Earth could be destroyed by tidal forces. Alternatively, if the Sun shrinks to a white dwarf before consuming Earth, the Earth would be too frigid to sustain life.