The nature and origin of highest-energy cosmic rays (cosmic rays with
energies of around 10²⁰ eV) are outstanding mysteries in physics: How
did they gain such extreme energies? Where did they come from? What
particles are they? The Telescope Array (TA) experiment challenges
these questions by measuring the energy, composition, and arrival
direction anisotropy of ultra-high-energy cosmic rays with energies
exceeding 10¹⁸ eV. TA is located in the desert in Utah, USA, and the
largest extensive-air-shower cosmic-ray detector in the northern
hemisphere. It consists of a surface array of 507 scintillation
counters covering approximately 700 km² and 38 fluorescence telescopes
located at three sites looking inward over the surface array. Its
hybrid operation started in March, 2008. Here I present the results
from TA using data collected over a 5-year period and the prospect.